<?php

class Lingua_Stem_Ru {

  var $VERSION = "0.02";
  var $Stem_Caching = 1;
  var $Stem_Cache = array();
  var $VOWEL = '/аеиоуыэюя/';
  var $PERFECTIVEGROUND = '/((ив|ивши|ившись|ыв|ывши|ывшись)|((?<=[ая])(в|вши|вшись)))$/';
  var $REFLEXIVE = '/(с[яь])$/';
  var $ADJECTIVE = '/(ее|ие|ые|ое|ими|ыми|ей|ий|ый|ой|ем|им|ым|ом|его|ого|ему|ому|их|ых|ую|юю|ая|яя|ою|ею)$/';
  var $PARTICIPLE = '/((ивш|ывш|ующ)|((?<=[ая])(ем|нн|вш|ющ|щ)))$/';
  var $VERB = '/((ила|ыла|ена|ейте|уйте|ите|или|ыли|ей|уй|ил|ыл|им|ым|ен|ило|ыло|ено|ят|ует|уют|ит|ыт|ены|ить|ыть|ишь|ую|ю)|((?<=[ая])(ла|на|ете|йте|ли|й|л|ем|н|ло|но|ет|ют|ны|ть|ешь|нно)))$/';
  var $NOUN = '/(а|ев|ов|ие|ье|е|иями|ями|ами|еи|ии|и|ией|ей|ой|ий|й|иям|ям|ием|ем|ам|ом|о|у|ах|иях|ях|ы|ь|ию|ью|ю|ия|ья|я)$/';
  var $RVRE = '/^(.*?[аеиоуыэюя])(.*)$/';
  var $DERIVATIONAL = '/[^аеиоуыэюя][аеиоуыэюя]+[^аеиоуыэюя]+[аеиоуыэюя].*(?<=о)сть?$/';

  function s(&$s, $re, $to)
  {
      $orig = $s;
      $s = preg_replace($re, $to, $s);
      return $orig !== $s;
  }

  function m($s, $re)
  {
      return preg_match($re, $s);
  }

  function stem_word($word)
  {
      $word = mb_strtolower($word);
      //$word = strtr($word, 'ё', 'е');
      # Check against cache of stemmed words
      if ($this->Stem_Caching && isset($this->Stem_Cache[$word])) {
          return $this->Stem_Cache[$word];
      }
      $stem = $word;
      do {
        if (!preg_match($this->RVRE, $word, $p)) break;
        $start = $p[1];
        $RV = $p[2];
        if (!$RV) break;

        # Step 1
        if (!$this->s($RV, $this->PERFECTIVEGROUND, '')) {
            $this->s($RV, $this->REFLEXIVE, '');

            if ($this->s($RV, $this->ADJECTIVE, '')) {
                $this->s($RV, $this->PARTICIPLE, '');
            } else {
                if (!$this->s($RV, $this->VERB, ''))
                    $this->s($RV, $this->NOUN, '');
            }
        }

        # Step 2
        $this->s($RV, '/и$/', '');

        # Step 3
        if ($this->m($RV, $this->DERIVATIONAL))
            $this->s($RV, '/ость?$/', '');

        # Step 4
        if (!$this->s($RV, '/ь$/', '')) {
            $this->s($RV, '/ейше?/', '');
            $this->s($RV, '/нн$/', 'н');
        }

        $stem = $start.$RV;
      } while(false);
      if ($this->Stem_Caching) $this->Stem_Cache[$word] = $stem;
      return $stem;
  }

  function stem_caching($parm_ref)
  {
      $caching_level = @$parm_ref['-level'];
      if ($caching_level) {
          if (!$this->m($caching_level, '/^[012]$/')) {
              die(__CLASS__ . "::stem_caching() - Legal values are '0','1' or '2'. '$caching_level' is not a legal value");
          }
          $this->Stem_Caching = $caching_level;
      }
      return $this->Stem_Caching;
  }

  function clear_stem_cache()
  {
      $this->Stem_Cache = array();
  }
}

?>